1. Technical Field
In brief, however, the present invention relates couplers for attaching an accessory, such as an excavator bucket, to an excavator arm of an excavator. Generally a coupler will comprise one or two jaws (or grooves, hooks or slots) and one or two latches for selectively securing (or releasing) one or two attachment pins of the accessory in the or each jaw (or groove, hook or slot).
2. Description of Related Art
Many couplers have been developed in the art. Some are fully automatic, i.e. fully operable from within the cab of the excavator for both coupling and decoupling an accessory to or from the coupler and some are part automatic/part manual, requiring many or most operations for coupling and decoupling of an accessory to or from the coupler to be carried out from within the cab, but with one or more operations needing to be done instead at the coupler itself.
A part automatic and part manual coupler is disclosed in GB2359062. The coupler is attached remotely to the accessory, i.e. from within the cab of the excavator. However, that attachment is made more secure by an additional manual step—the insertion of a safety pin into a position behind a pivoting latching hook of the coupler.
A fully automatic coupler is disclosed in GB2330570. It has a gravity operated blocking bar that is designed to fall behind the rear latching hook during normal use, whereby when the coupler is in use, and therefore in a normal, in-use or upright, orientation, the latching hook is prevented from being retracted by the presence of the blocking bar behind the latching hook. To release the accessory, however, that blocking bar is lifted from that blocking position either by a second hydraulic ram (i.e. one that is not connected to the latching hook) or simply by inverting the coupler, i.e. by moving the excavator arm and coupler into either the crowd position or to a position curled above the excavator arm (an unconventional position for an excavator arm to assume). In that inverted orientation, the blocking bar will fall away from its blocking position to allow the latching hook for the rear attachment pin then to be retracted by the latching hook's own hydraulic ram.
There are also many other couplers, either fully automatic or part automatic and part manual. See, for example, the couplers disclosed in the following publications: Australian Patent AU557890, German Utility Model DE20119092U, European Patent Applications EP0405811 and EP1318242, GB Patent Application GB2332417, U.S. Pat. Nos. 5,692,325 and 6,132,131, and PCT Publication WO99/42670.
The majority of prior art couplers have a first (or top) half that is for attaching the coupler to the excavator, and that attachment is generally to an excavator arm of the excavator. The coupler of EP0405813, however, is instead for attaching a digger bucket to the front end loader of the excavator. The couplers then have on the other or opposite side of the coupler two attachment pin engaging jaws, grooves, hooks or slots, whereby an accessory having a pair of attachment pins (such as an excavator bucket) can be attached to that coupler via the pair of attachment pins: one of the jaws, grooves, hooks or slots is for engaging a first or front attachment pin of the accessory and the other jaw, groove, hook or slot is for engaging the second or rear attachment pin of the accessory.
Couplers are also known for attaching accessories that have only one attachment pin. Those couplers have just one jaw, groove, hook or slot. Typically, however, the accessory then has the other jaw, groove, hook or slot for engaging a second attachment pin, which is instead positioned on the coupler.
Despite the existence of numerous designs of coupler, there is still an ever increasing demand upon the industry for the provision of even more security for fully automatic couplers, and for which couplers no manual steps need to be carried out by the user on the coupler for completing the securement or detachment of an accessory. A purpose for this drive is that it allows the user to remain within the safe environment of the cab of the excavator. This is important since accessories and couplers are typically quite large and heavy pieces of equipment, and thus they are potentially dangerous when being manipulated by an excavator.
For couplers having a pair of jaws, one of the jaws usually faces downwards, i.e. away from the first half of the coupler, and that jaw is usually referred to as the rear jaw—it is normally located, in use, the furthest away from the cab, and excavator arms usually extend from a rear of the excavator. Due to its position, and the way it faces in use, often that jaw is not visible from the cab. The other jaw, however, usually faces away from that rear jaw and towards the cab. It generally is also rotated by approximately 90° relative to the rear jaw, i.e. instead of pointing downwards, it usually points forwards. It is usually, in use, nearer to the cab than the rear jaw and thus it is usually referred to as the front jaw.
In many such prior art couplers a pivoting or sliding latching hook or latching plate is provided for the rear jaw for locking an attachment pin within that jaw. Thus, to couple the accessory to the coupler, a first or front attachment pin is first engaged into an open front jaw of the coupler, and the coupler is then rotated or manipulated relative to the accessory to position the second attachment pin into the coupler's open rear jaw. Then the latching hook or latching plate is driven rearwardly, for example by a hydraulic piston or a screwthread, to close the rear jaw to lock the rear attachment pin within the rear jaw. That in turn locks the front attachment pin in the front jaw.
Such a securement of the accessory to the coupler is entirely secure, subject to there being no failure of the respective components of the coupler. However, users of such couplers additionally demand back-up safety mechanisms to be incorporated into those couplers to provide assurances that an accessory cannot accidentally be decoupled from a coupler, even if the drive mechanism for the latching hook or the latching plate is accidentally retracted or in the event of a mis-use of the coupler, or even in the event of a failure of a component of the coupler or the accessory. Further, there is a drive towards making the back-up safety features both automatic to implement and visible from within the cab. By being automatic, they cannot be omitted or forgotten by the user, and by being visible from the cab it is possible to assess their status from the cab, i.e. to carry out a remote visual check as to whether the safety features have adopted their correct back-up safety position for ensuring a backed-up securement between the coupler and the accessory. Further, the demand is for such couplers that still allow fully automatic coupling and decoupling of the accessory from the coupler.
It should also be observed that many prior art couplers have the provision for accommodating different accessories, i.e. ones having different distances between their respective attachment pins. That allows accessories from different manufacturers, or from different product ranges, to be accommodated by the coupler (it is commonplace for different buckets and other accessories from different manufacturers to have different distances between their pairs of attachment pins, i.e. different pin spacings). Prior art couplers generally achieve that by the provision of either a screwthread drive system or a hydraulic ram mounted between the two jaws, grooves, hooks or slots. The screwthread or a hydraulic ram can then move one or both of the jaws, grooves, hooks or slots relative to a frame of the coupler to accommodate the different pin spacings. Generally speaking, however, just one of the jaws, grooves, hooks or slots is moved by the screwthread or hydraulic ram, and that one is most frequently the rear one (or the latch associated therewith).
The securement of the two attachment pins within the two jaws is generally by a relative separation of the two pin-engaging components. That securement of the two fixed attachment pins of the accessory within the two jaws of the coupler can be referred to as a primary securement since it alone provides a securement of the accessory to the coupler. Such primary securement mechanisms are strong and thus are generally reliable since it is most unlikely that a component of it, such as either the screwthread or the hydraulic ram, or the hook or jaw themselves, will fail. That is because these items are all designed to meet the demands of the usual environment of use for the coupler. Indeed, these items are often “over-engineered” to provide a significant overload buffer). Despite that, however, it is usual to provide the above mentioned back-up safety (or failsafe) mechanisms to prevent the accessory from decoupling from the coupler in the unlikely event of such a failure.
Such safety back-up mechanisms, as known in the art, include at a most simple level, just a cover for the actuation circuit (usually in the cab of the excavator). That prevents accidental access to the actuation switches during use of the accessory. However, there is a demand for additional security. As such, failsafe mechanisms are provided in or on the coupler itself. See, for example, the coupler of EP1318242. It has a spring driven hook for the front jaw, which hook defaults to a closed state for securing a front attachment pin within the front jaw of the coupler. Therefore, even if the rear hook fails, the accessory is secured within the coupler. A problem with that coupler, however, is that if the decoupling command is given accidentally, the spring driven hook will automatically be retracted by the hydraulic ram as the sliding rear jaw reaches a fully retracted position. U.S. Pat. No. 6,132,131 and U.S. Pat. No. 5,692,325 similarly provide a latching hook for the front jaw that is driven by the rear jaw's hydraulic ram, and as such they also have that same problem. In GB2332417, however, a toggling dual-hook arrangement is provided—there are two moving hooks that are interconnected by a toggling arrangement to ensure that as one hook opens the other hook closes, and vice versa. This prevents both hooks from opening simultaneously. However, if either the link or one of the hooks fails, the coupling between the accessory and the coupler becomes vulnerable.